Whether it's a festival stage, a performing arts center, a dive bar or a late night campground set, Boulder Acoustic Society will deliver musical diversity throughout their set.

Old school but never old, the Colorado-based Boulder Acoustic Society is riding the new wave of American roots music. It's what happens when four songwriters get together to mash up blues, folk, gospel, indie and world music to soothe their musical curiosities. Whether it's a festival stage, a performing arts center, a dive bar or a late night campground set, Boulder Acoustic Society will deliver musical diversity throughout their set.

Dale Bridges of the Boulder Weekly call the band "experimental, but not pretentious. Fun and serious in all the right places. Weird, but not in a 'look at how weird I am' way."

Nate Harper of Scene magazine wrote that "The Boulder Acoustic Society get to do anything they want, largely because they say so. And by anything I mean yodeling during a rockabilly song, launching into a pretty killer David Byrne impression, or doing, in their own words, a minor key acoustic punk version of 'Maggie's Farm.' They can get away with this rampant eclecticism because they can pull it off, and while they walk the fine line between grating and experimental, they walk it quite well."

Kailin Yong, Aaron Keim, Scott McCormick and Scott Aller are the Boulder Acoustic Society.

Yong is from Singapore, via Vienna, New York, San Francisco and Denver, and he plays violin and ukulele and sings. He can play a Bach partita, rock a Brazilian choro, sing in Mandarin and play quarter-tone scales used in Hindu and Muslim cultures.

Keim plays bass, ukulele and banjo and sings, and he collects obscure folk songs and builds his own instruments. He plays Appalachian music on the banjo, ragtime on the ukulele and blues on steel guitar. He also slaps the bass like it owes him money.

McCormick found music in the gospel churches and the punk clubs of Chicago. He plays accordion, ukulele and piano and sings. He also plays modern jazz on the piano and gritty folk punk on the guitar. He can sing in Gaelic, and he's also the band's photographer and graphic designer.

Aller, on junkyard percussion and vocals, gave up his drum kit to play a makeshift wooden box, a washboard and other oddities with the Boulder Acoustic Society. He's the one with the Mohawk.

Even though the band has been around for about five years and is touring behind its fifth album — "Punchline," released in August on Nine Mile Records — the Boulder Acoustic Society is just now getting national attention. The group tried for perfection when recording its first two albums, "So Many Stars" in 2004 and "The 8th Track" in 2006. But perfect didn't cut it for the group, so the members began taking their new ideas about folk and bluegrass music and leaving enough rough edges while making the songs sound as good as they could.

The 15 songs on the new album include a sharp cover of Red Hot Chili Peppers' "Give It Away."

Colorado Music Buzz said of their latest release: "Gems of acoustic, Americana and pop workmanship abound here. To tell you which ones are better than the others would be rather fruitless. It's all good. With talent that harkens to practicing eight hours every day when you were a kid, BAS have finally showcased the immense musical vision they had started out with sometime ago. Even if you take the killer packaging away, it's still one of the most memorable, can't-stop-listening albums to ever come out of Colorado."

One edge that wasn't left rough was the packaging for "Punchline." Boulder Acoustic Society turned its new CD into an elaborate, pop-up, 3-D diorama depicting the band performing.

Earlier albums by the group include "The Caged Bird" (2008) and "Now" (2007).

While the band's name implies tradition, they push roots music with something interesting and adventurous at every turn, bringing a unique lineup to support sharp vocals and grooves.

All of it comes from four guys who wear vintage clothes, savor small-batch bourbon and rock the ukulele.